# std::abs, std::labs, std::llabs, std::imaxabs

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< cpp‎ | numeric‎ | math

Defined in header `<cstdlib>` |  |
Defined in header `<cmath>` |  |
int abs( int num ); | (1) | (constexpr since C++23)
long abs( long num ); | (2) | (constexpr since C++23)
long long abs( long long num ); | (3) | (since C++11) (constexpr since C++23)
Defined in header `<cstdlib>` |  |
long labs( long num ); | (4) | (constexpr since C++23)
long long llabs( long long num ); | (5) | (since C++11) (constexpr since C++23)
Defined in header `<cinttypes>` |  |
std::intmax_t abs( std::intmax_t num ); | (6) | (since C++11) (constexpr since C++23)
std::intmax_t imaxabs( std::intmax_t num ); | (7) | (since C++11) (constexpr since C++23)

Computes the absolute value of the integer number num. The behavior is undefined if the result cannot be represented by the return type.

If `std::abs` is called with an unsigned integral argument that cannot be converted to int by integral promotion, the program is ill-formed.

Overload (6) of `std::abs` for std::intmax_t is provided in `<cinttypes>` if and only if std::intmax_t is an extended integer type. | (since C++11)

### Parameters

num | - | integer value

### Return value

The absolute value of num (i.e. `|num|`), if it is representable.

### Notes

In 2's complement systems, the absolute value of the most-negative value is out of range, e.g. for 32-bit 2's complement type int, INT_MIN is -2147483648, but the would-be result 2147483648 is greater than INT_MAX, which is 2147483647.

### Example

Run this code

    #include <climits>
    #include <cstdlib>
    #include <iostream>

    int main()
    {
        std::cout << std::showpos
                  << "abs(+3) = " << std::abs(3) << '\n'
                  << "abs(-3) = " << std::abs(-3) << '\n';

    //  std::cout << std::abs(INT_MIN); // undefined behavior on 2's complement systems
    }

Output:

    abs(+3) = +3
    abs(-3) = +3

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 2192 | C++98 | overloads of `std::abs` were inconsistently declared in two headers | declared these overloads in both headers

### See also

abs(float)fabsfabsffabsl (C++11)(C++11) | absolute value of a floating point value (\(\small{|x|}\)|x|) (function)
abs(std::complex) | returns the magnitude of a complex number (function template)
abs(std::valarray) | applies the function abs to each element of valarray (function template)
C documentation for abs, labs, llabs

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